In an embedded magnet synchronous motor (so-called IPM motor) configured such that permanent magnets are embedded in a core (iron core) of a rotor, a structure has been proposed which prevents irreversible demagnetization of the permanent magnet.
A rotor is configured by inserting permanent magnets into a rotor core formed by laminating electromagnetic steel plates provided with a plurality of magnet holes. A gap portion (flux barriers) communicating with the magnet holes and configured to prevent irreversible demagnetization are provided on end parts of the magnet holes, into which the magnets are to be inserted, in a circumferential direction of the rotor (end parts in a rotating direction).
In a rotor disclosed in JP2008-148391A, a flux barrier includes an outer periphery proximate part closer to a rotor outer periphery than a part of a permanent magnet closest to the rotor outer periphery and is shaped to have a part distant from the rotor outer periphery on a rotor inner peripheral side with respect to an extension line of an outer part of the permanent magnet between the outer periphery proximate part and the part of the permanent magnet closest to the rotor outer periphery. Thus, a magnetic flux propagating from a q-axis side end part of the permanent magnet toward the flux barrier propagates toward a position between the outer periphery proximate part and the rotor outer periphery after entering a core of a rotor from the flux barrier. As a result, the propagation of the magnetic flux in a direction to disturb an arrangement direction of a magnetic dipole of the permanent magnet is suppressed and irreversible demagnetization hardly occurs.